Electromagnetic control device



April 1940- F. H. WINTER 2,196,883

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Filed Jan. 29, 19 9 inventor": Fred H. Winter;

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Patented Apr. 9, 1940 PATENT OFFICE ELECTROMAGNETIC CONTROL DEVICE rm: 11. Winter, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application January 29, 1938, Serial No. 187,753

4: Claims.

devices and has for its object a simple and reliable electromagnetic device for general purposes of time delay control which will afford a substantial 5 time delay interval in-performing a control function.

Particularly valuable for use in the control of synchronous motors and for the acceleration of other electric motors, although I do not intend to be limited thereto, my invention permits a substantial reduction in the cost of the equipment and the control panel wiring heretofore required. With a device built in accordance with my invention, time delays in operation as high as 3 to 4 seconds have been obtained fairly constantly. It is believed that time delays of 1 seconds may be a practical value obtainable even with changes in balance of the device due to residual magnetism in the frame and variations in the energization 20 current.

For a more complete understanding of my invention, reference should be had to the accompanying drawing, Fig. 1 of which is a front elevation view of one embodiment of my invention 25 showing an auxiliary energization winding for purposes of regulation; Fig. 2 is a front elevation view of another embodiment of my invention which may be constantly energized during operation; and Fig. 3 is a front elevation of a motor 0 control system having a variable resistance in the shunted winding which is operated by the movement of the armature element.

Referring to Fig. 1, I have shown my invention in one form as comprising a magnetic frame I!) having the four legs ll, l2, I3 and I4 cooperating with which is an armature element l5 carrying a contact I 6 which is movable to engage a stationary contact ll for controlling a circuit (not shown). The armature element l5 having two straight portions at a small angle with each other is pivotally mounted at the junction of these portions on the upper end of the leg IS in good magnetic contact therewith. Two positions may be assumed by the armature element l5, first, when it is in 45 contact with the upper faces of the legs l3 and It in the position shown, and second, when it is in contact with the upper faces of the legs ll, I2, and I3 after pivotal movement from its first position. For energizing the frame II), the leg I2 is provided with a main energizing winding I8 which may be connected to a suitable source of direct current by a switch IS. The leg I3 is provided with a winding 20 shunted by a variable resistance 2| connected in series therewith. The leg l3 also 55 carries an auxiliary winding 22 wound to oppose,

(Cl. 175-320) My invention relates to electromagnetic controlv when energized, the magnetic flux set up in the leg l3 by the winding 20. This auxiliary winding 22 may be connected in parallel with the winding l8 by a separate switch 23. The armature element I5 is biased to the first position shown by a 5 spring 24 which is carried by an angle support 25 attached to the right end of the armature element I5.

The magnetic circuits of the device by which time delays in operatiton are effected comprise 10 two parallel circuits. The primary magnetic circuit includes the attracting leg l2, the middle leg 13 and the connecting portion of the frame ill and armature I 5 between these legs. The secondary magnetic circuit includes the attracting 15 leg I 2, the leg I4 and the connecting portion of the frame In and armature I5 between these legs. When the winding I8 is energized, substantially all of the flux in the frame flows through the leg l2 and across the air gap to seek to attract the armature I 5 to its attracted position. Temporarily, however, the effective reluctance of the primary magnetic circuit is increased by the counter effect of the short circuited winding 22 on the flux seeking to enter the leg l3, the effective 25 reluctance of the secondary magnetic circuit,

however, not being increased. In this manner, a certain part of the flux is forced into the relatively low reluctance shunt path of the secondary magnetic circuit, namely, the leg I4 and the right end of the frame l0 and armature 15. In this manner, a strong magnetic force develops at the end of the leg l4 tending to hold the armature IS in the unattracted position shown. Obviously, the greater the flux that is forced through the shunt path, the greater is the temporary attraction on the armature l5 and preferably. as shown, the reluctance of the shunt path is low compared with that of the primary magnetic circuit when the armature is in its unattracted position. This tends to keep the reluctance of the whole device down. Time delays of one or more seconds duration require essentially low reluctance magnetic circuits and high flux in order to make the short circuited winding 22 effective in shifting a suflicient flux to the leg M to lock the armature I 5 in the unattracted position for such a substantial time interval.

In operation of the device, the winding I8 is energized by closing the switch IS, the switch 23 remaining open. Magnetic flu'xbuilds up in the frame I 0 which seeks to attract the armature element l5 to its second position to close the contacts l6 and H. The flow of flux in the leg I3 is opposed, however, by the shunted winding 2|, 5

which opposes any fiux change in the leg i3. and the fiux in the right half of the frame i0 is thereby caused to complete its return circuit to the leg 12 by flowing through the leg l4, through the armature element l5, and across the air gap between the armature E5 and the leg (2. The armature element 5 is thereby attracted to the leg M. This magnetic attraction together with the bias of the spring 24 tends to hold the armature element l5 in its first position against the attraction of the legs if and [2. The movement of the armature element l5 to its second position is delayed until the flux is enabled to fiow freely in the leg I3, through the armature element (5, back to the leg 52. When the flux is enabled to flow freely in the leg l3, the greater part of the flux in the right hand side of the frame [0 no longer passes through the leg i4, and the magnetic attraction between the leg i4 and the right arm of the armature element I5 is weakened sufficiently to permit the armature element l5 to move to its second position, since the magnetic attraction of the legs l2 and i3 is greater than the bias of the spring 24. A time delay pick-up of the armature element 15 from its first position to its second position is thereby effected. With the armature element E5 in its second position, the winding l8 may be de-energized by opening the switch IS. The return of the armature 5 to its first position is delayed by the shunted winding 20 which again opposes any change in flux and causes the flux flowing in the legs 12 and I3 to persist so that the armature i5 is attracted to its second position for a substantial time interval before the bias of the spring 24 is sufficient to move the armature l5 back to its first position.

Sometimes, particularly in connection with the synchronizing of synchronous machinery, it may be desirable to retain the last mentioned time delay feature only for a short period of time after the armature 15 has moved to its second position and if the switch [9 is opened thereafter, to provide for characteristic fast relay operation. In such a case, the switch 23 may be closed simultaneously with the closing of the contacts 6 and I1 to energize the auxiliary energization winding 22, the switch 23 if desired being suitably, mechanically or electrically interlocked with the armature I5 for closure with the contacts 16 and [1. Also the switch 23 may be closed any time after the closure of the contacts l6 and I! whenever the particular operation characteristic is wanted. The winding 22 is excited from the same source as the winding l8 and is wound on the leg l3 in a direction to produce in the leg 13 a counter flux to the flux generated by the main Winding I8, the winding 22 having a number of turns sufficient to bring the flux in the leg l3 to a zero value after a predetermined time under all values of voltage across these windings. Since it takes some time for the flux produced by the winding 22 to reduce the flux in the leg 13 to a zero value, if the switch i9 is opened during this time before the flux reaches a zero value and the armature element [5 tries to immediately return to its first position, it will be temporarily delayed by the flux remaining in the leg l3. After the winding 22 has been energized for a predetermined time sufiicient to reduce the fiux in the leg l3 to a zero value, however, the flux fiows only in the legs H and i2 in a fast magnetic circuit. If switch [9 is then opened, a condition of fast drop-out ensues and the armature element 55 returns to its first position from its second position without a time delay. Ihus it is seen that whenever a fast movement of the armature element l5 from its second position to its first position is desired, the winding 22 may be energized by closing the switch 23, and after the fiux in the leg i3 is reduced to a zero value a fast dropout characteristic pertains.

The desired time delay interval of operation may be accurately adjusted in several ways. Shims of non-magnetic material of varying thicknesses may be used to maintain a definite air gap between the arms of the armature element and the points of contact with the frame in the two positions. The use of these shims will also assist in avoiding the effects of residual magnetism in the frame. The tension of the biasing spring may be adjusted for varying the force necessary to overcome its bias. Further. the choking effect of the shunted winding on the change in fiux may be varied by the addition of a resistance in series with this winding. I prefer to use a variable resistance in the shunted winding circuit which may be increased to obtain a corresponding decrease in the time delay and which may be decreased for a corresponding increase of the time delay.

Referring now to Fig. 2, it will be observed that in this form the device comprises a frame 30 having the three legs 3!, 32, and 33. For energizing the frame 30, a main energization winding 34 being supplied from a suitable source of direct current 42 is provided on the leg 3i and is connected in series with an auxiliary energization winding 35 on the leg 32 having in series therewith a variable resistance 31. The auxiliary winding 35 is arranged to be shunted by a line switch 36 and is wound so that the flux generated in the leg 32 is normally opposed to the flux generated in the leg 3| by the winding 34 when the windings 34 and 35 are energized. Although I prefer to energize the frame 30 by means of main energizing winding 34 on leg 3|, I do not intend to be limited thereto. It will be obvious to one skilled in the art that the frame 30 may readily be energized by a leg made from some good permanent magnet material such as that disclosed in the United States Patent 1,947,274 to W. F. Ruder which issued on February 13, 1934, and is assigned to the present assignee. This permanent magnet alloy consists essentially of iron, nickel, and aluminum and has the magnetic properties of a high coercive force and high residual magnetism. A contact 39 carried by an armature element 38 is movable to engage a stationary contact 43 for controlling a circuit (not shown). The armature element 38 having two straight portions at a slight angle with each other is pivotally mounted on the upper face of the leg 32 in good magnetic contact therewith. One or more guide projections 44 may be provided on the end of the leg 32 to improve the magnetic contact between the armature element 38 and the leg 32 and assist in keeping the armature element 38 in alignment with the legs 3| and 32. Two positions may be assumed by the armature element 38, first, when it is in contact with the upper faces of the legs 32 and 33 as shown, and second, when it is in contact with the upper faces of the legs 3i and 32. The armature element 38 is biased to its first position by a spring 40 connected to an angle support 4| which isfastened to the right end of the armature element 38.

When the windings 34 and 35 are energized from the source 42, the energization is sufiicient to build up a flux in the legs 32 and 33 to saturation; The armature element 36 is held in its first position by the attraction of leg 33 and the bias of the spring 40. When the line switch 36 is closed, the auxiliary winding 35 is shunted, and the main winding 34 is energized to full value. The flux gradually dies out in the right hand magnetic circuit comprising the right end portion of frame 30, the leg 33, the armature element 38, and the leg 32 and gradually reverses in the leg 32 against the choking effect of the shunted winding 35. The armature element 38 is enabled to close to its second position only after a complete decay of flux in the leg 32 and a building-up of the flux in that leg in the opposite direction. Thus a time delay interval in the movement of the armature element 38 from its first position to its second position is efiected. The variable resistance 31 is available to vary the Value of the winding 35 so that the duration of this time delay interval may be adjusted. When the armature element 36 is in its second position and the line switch 36 is opened, a forced reversal of flux occurs and the relay returns to its first position with not substantial delay.

Referring to Fig. 3, I have shown a device com prising a further embodiment of my invention for shunting out a starting resistance 58 of a direct current motor 60. This device comprises a frame having the three legs 5| 52, 53 and an armature element 54 pivotally mounted on the end of the middle leg 52 in good magnetic contact therewith. The armature element 54 may assume two positions in its pivotal movement, first, when it is in contact with the upper faces of the legs 5| and 52 as shown, and second, when it is in contact with the upper faces of the legs 52 and 53. The armature element 54 is biased to its first position by a spring 55 connected to angle support 56 which is carried by the left end of the armature 54. A movable contact 51 is carried by the armature 54 and is arranged to engage a stationary contact 58, when the armature element 54 is in its second position, for shunting out the starting resistance 59 of the motor 68 through a conductor 6| which is electrically connected to the contact 5'! and a conductor 69 connected to the contact 56. For energizing the frame 50, an energization winding 62 on the leg 53 may be connected in parallel with a conductor 63 which feeds the motor 66 through a double pole switch 64 from a suitable source of direct current. The leg 52 of the frame 50 is provided with winding 65 which is shunted by a variable resistance 66 in series connection therewith. The resistance value of the variable resistor 66 is arranged for independent adjustment by means of interlock contacts 61 in each of the two positions of the armature element 54. The contact bar of the contacts 61 is operated by the movement of the armature element 54 and a connecting rod 68 which may be suitably fastened to the righthand portion of the armature element 54. A condition of fast or slow pick-up and fast or slow drop-out of the armature element 54 may be obtained by varying the choking eifect of the winding 65 by appropriate settings of the variable resistance 66. Upon closing the switch 64, current flows to the motor 66 through the conductor 63 and to the starting resistance 58 as well as to the energization winding 62. The flux built up in the frame'50 is temporarily denied entrance to the leg 52 by the shunted winding 65, therefore, it seeks the next best path, that is, through the leg 5|, the armature element 54, and across the air gap from the armature element 54 to the leg 53. The magnetic attraction of the leg SI for the armature element 54 and the bias oi the spring 55 cooperate to hold the armature 54 in its first position until the choking efiect of the winding 65 is overcome. Gradually the fiux is permitted to flow freely in the leg 65 and complete the magnetic circuit in the right-hand portion of the frame comprising the leg 62, the frame 50, the leg 65, and the armature element 54 to cause the flux in the leg 5| to fall to a low value. The armature 54' then moves to its second position to close the contacts 51 and 58 and shunt out the starting resistance 59. The duration of the time delay interval is readily adjustable by varying the resistance 66 in the shunted winding 65. The greater the resistance in this circuit, the less will be the choking effect of the winding, and the less will be the time delay interval. As illustrated in the drawing, the circuit comprising the shunted winding 65, the upper pair of contacts 61, and the contact bar in its upper position is such that the variable resistance 66 is nearly completely out oi the circuit, and so the greatest time delay interval prevails on pick-up of the armature 54 from its first position to its second position.

With the armature 54 in its second position, when the switch 64 is opened, the shunted winding 65 assists in making the flux persist in the legs 52 and 53, the connecting portion of the frame 5|), and the right arm of the armature element 54. The armature 54 is thereby maintained in its second position for a time interval until the magnetic attractionof the leg 53 is overcome by the spring 55, and the armature 54 is enabled to return to its first position. The desired time delay interval is obtained by adjusting the value of the resistance 66 in the circuit including the winding 65, the lower pair of contacts 61, and the contact bar in its lower position.

While I have shown a particular embodiment of my invention, it will be understood, of course. that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is: Y

1. An electromagnetic control device comprising a magnetic frame having at least three legs, an armature element mounted for pivotal movement on the middle leg to be attracted to one leg in a first position and to be attracted to the other leg in a second position, control means operable by said armature element, means to bias said armature element toward said first position, means on said other leg for energizing said frame withv a primary fiux. an auxiliary energizing winding on said middle leg adapted to generate a flux opposing said primary flux for causing said armature to be attracted to said first position, means for shunting said auxiliary winding, said auxiliary winding then acting as a shunted coil for introducing a predetermined time interval in the movement of said armature from said first po ition to said second position.

2. An electromagnetic control device comprising a magnetic frame having three legs, an arma ture element mounted for pivotal movement on the middle leg to be attracted to one leg in a first position and to be attracted to the other leg in a second position, switching means operable by said armature element, means to bias said armature element toward said first position, a main energizing winding for said frame on said other leg,

a second energizing winding on said middle leg in series with said main energizing winding, means for shunting said second winding and thereby energizing said main winding to its full value, means including a variable resistance in series with said second winding for adjusting its value as a choke, said second winding acting as a shunted coil for introducing a predetermined time interval in the movement of said armature from said first position to said second position.

3. An electromagnetic control device comprising a magnetic frame having a plurality of legs, a magnetic armature element mounted for pivotal movement between two positions cooperating in a first of said positions with said frame to form a first magnetic circuit with a portion of said frame and cooperating in a second of said positions to form a second magnetic circuit with another portion of said frame, means including a winding on one of said legs for energizing said frame, means for biasing said armature element to said first position, means including a second winding in series with said energizing winding on another of said legs to generate a counter flux in said frame which cooperates with the flux generated by said first energizing winding and said biasing means in holding said armature element in said first position, means for shunting said second winding and energizing said first winding to its full value, said second winding then becoming a shunted winding whose induced fiux gradually decays and reverses and permits said armature element to be attracted to said second position after a substantial time delay from the moment of shunting out said second winding, and switching means operable by said armature element.

l. An electromagnetic control device comprising a magnetic frame having at least three legs including an attracting leg, a middle leg, and a third leg, said middle leg being positioned between said attracting leg and said third leg, a pivoted armature having a pair of extending ends movable between normally attracted and unattracted positions, a first of said ends of said armature being spaced by an air gap from said attracting leg and a second of said ends of said armature being disposed adjacent said third leg of said frame when said armature is in said unattracted position, said armature and said three legs of said frame forming a pair of parallel magnetic circuits comprising a primary magnetic circuit including said attracting leg, said middle leg, and said first end of said armature, and a secondary magnetic circuit including said at tracting leg, said third leg and both ends of said armature, said primary magnetic circuit inherently being of lesser reluctance than the reluct ance of said secondary magnetic circuit, means for energizing said frame to cause substantially all of the ii a in said magnetic circuits always to fiow through said attracting leg and across said air gap thereby to pivot said armature to said attracted position with said first end adjacent said attracting leg and said second end spaced by an air gap from said third leg of said frame, means including a short circuited winding on said middle leg for temporarily increasing the effective reluctance of said primary magnetic circuit without increasing the effective reluctance of said secondary circuit when said frame is magnetically energized, the effective reluctance of said primary magnetic circuit then being of sufiicient magnitude relative to the reluctance of said secondary magnetic circuit to cause flux to flow in said secondary magnetic circuit for magnetically attracting said armature at said third leg to hold said armature in its normally unattracted position for a predetermined time interval, biasing means for biasing said armature to its normally unattracted position and for cooperating with the temporary magnetic attraction on said armature at said third leg to retain said armature in said normally unattracted position until the effective reluctance of said primary magnetic circuit is decreased sufiiciently to cause the flux to shift to said primary magnetic circuit and cause said armature to be pivoted to its attracted position, and control means operated by said armature.

'5. An electromagnetic control device comprising a magnetic frame having at least three legs including an attracting leg, a middle leg, and a third leg, said middle leg being positioned between said attracting leg and said third leg, a pivoted armature having a pair of extending ends movable between normally attracted and unattracted positions, a first of said ends of said armature being spaced by an air gap from said attracting leg and a second of said ends of said armature being disposed adjacent said third leg of said frame when said armature is in said unattracted position, said armature and said three legs of said frame forming a pair of parallel magnetic circuits comprising a primary magnetic circuit including said attracting leg, said middle leg, and said first end of said armature, and a secondary magnetic circuit including said attracting leg, said third leg and both ends of said armature, said primary magnetic circuit inherently being of lesser reluctance than the reluctance of said secondary magnetic circuit, both of said magnetic circuits being of relatively low reluctance to permit a large fiow of flux in said frame, means for energizing said frame to cause substantially all of the flux in said magnetic circuits always to fiow through said attracting leg and across said air gap thereby to pivot said armature to said attracted position with said first end adjacent said attracting leg and said second end spaced by an air gap from said third leg of said frame, means including a short circuited winding on said middle leg for temporarily increasing the effective reluctance of said primary magnetic circuit without increasing the effective reluctance of said secondary magnetic circuit when said frame is magnetically energized. the effective reluctance of said primary magnetic circuit then being of sufficient magnitude relative to the reluctance of said secondary magnetic circuit to cause fiux to fiow in said secondary magnetic circuit for magnetically attracting said armature at said third leg to hold said armature in its normally unattracted position for a predetermined time interval, biasing means for biasing said armature to its normally unattracted position and for cooperating with the temporary magnetic attraction on said armature at said third leg to retain said armature in said normally unattracted position until the effective reluctance of said primary magnetic circuit is decreased sufiiciently to cause the flux to shift to said primary magnetic circuit and cause said armature to be pivoted to its attracted position, and control means operated by said armature.

6. An electromagnetic control device comprising a magnetic frame having at least three legs including an attracting leg, a middle leg, and a third leg, said middle leg being positioned between said attracting leg and said third leg,

a pivoted armature having a pair of extending ends movable between normally attracted and unattracted positions, a first of said ends of said armature being spaced by an air gap from said attracting leg and a second of said ends of said armature being disposed adjacent said third leg of said frame when said armature is in said unattracted position, said armature and said three legs of said frame forming a pair of parallel magnetic circuits comprising a primary magnetic circuit including said attracting leg. said middle leg, and said first end oi. said armature, and a secondary magnetic circuit including said attracting leg, said third leg and both ends of said armature, a portion of said secondary magnetic circuit including said third leg and said second attracted position with said first end adjacent said attracting leg and said second end spaced by an air gap from said third leg of said frame,-

means including a short circuited winding on said middle leg for temporarily increasing the effective reluctance of said primary magnetic circuit without increasing the effective reluctance of said magnetic circuit when said frame is magnetically energized, the efi'ective reluctance of said primary magnetic circuit then being of sufficient magnitude relative to the reluctance of said secondary magnetic circuit to cause flux to flow in said secondary magnetic circuit for magnetically attracting said armature at said third leg to hold said armature in its normally unattracted position for a predetermined time interval, biasing means forv biasing said armature to its normally unattracted position and for cooperating with the temporary magnetic attraction on said armature at said third leg to retain said armature in said normally unattracted position until the effective reluctance of said pri mary magnetic circuit is decreased sufliciently to cause the flux to shift to said primary magnetic circuit and cause said armature to be pivoted to its attracted position, and control means operated by said armature.

- FRED H. WINTER. 

